A top Democrat in the US Congress has vowed to look into a report that US President Donald Trump ordered his personal lawyer to lie to Congress to hide dealings with Russia.

Adam Schiff, who heads the Intelligence Committee in the House of Representatives, was reacting to a report by the online site BuzzFeed that Mr Trump ordered lawyer Michael Cohen to lie to Congress in 2017 about talks to build a Trump Tower in Moscow during the 2016 presidential campaign.

“The allegation that the President of the United States may have suborned perjury before our committee in an effort to curtail the investigation and cover up his business dealings with Russia is among the most serious to date,” Mr Schiff tweeted.

“We will do what’s necessary to find out if it’s true.”

Mr Trump also supported a Cohen plan to visit Russia during the presidential campaign to meet President Vladimir Putin to jump-start the Moscow tower negotiations according to BuzzFeed, which cites two unnamed federal law enforcement officials as sources.

The trip never materialised, and Mr Trump has repeatedly and emphatically denied dealings with Russia during the campaign.

Cohen also provided Mr Trump and two of his children — Ivanka and Donald Trump Jr. — regular updates about the Moscow project, the sources told BuzzFeed.

A spokesperson for Ms Trump rejected the report.

“Ms Trump did not know about this proposal until after a non-binding letter of intent had been signed, never talked to anyone outside the organisation about the proposal, never visited the projected project site and was only minimally involved,” the spokesperson said in a statement.

Cohen, who was the real estate billionaire’s right-hand-man and fixer at his umbrella company the Trump Organisation, in New York at the time, pleaded guilty last year to several charges including the violation of campaign finance laws by arranging hush payments ahead of the 2016 election to women who alleged extramarital affairs with Mr Trump.

Cohen also pleaded guilty to lying to Congress by stating that the Trump Moscow project ended in January 2016, long before Mr Trump became the Republican presidential nominee, when it actually extended into June 2016.

The New York lawyer, 52, was sentenced to three years in jail for the campaign finance violation and other charges.

His incarceration has been delayed while he provides support to ongoing investigations into possible Trump campaign collusion with Russia and Mr Trump’s finances.

Cohen is scheduled to testify to the House Oversight Committee, newly controlled by opposition Democrats, on February 7 about his work for Mr Trump.

Mr Trump, however, labelled his former lawyer a liar on Twitter.

Meanwhile, Democratic House Speaker Nancy Pelosi is cancelling a congressional fact-finding trip to Afghanistan and claiming the White House leaked her plans to fly commercial.

The announcement by Ms Pelosi’s office came a day after President Donald Trump nixed Ms Pelosi’s plans to take a military aircraft to Afghanistan.

Spokesman Drew Hammill says Ms Pelosi and accompanying politicians were prepared to take a commercial flight but cancelled after the State Department warned that publicity over the visit had “significantly increased the danger to the delegation and to the troops, security, and other officials supporting the trip.”

The President’s move to cancel the military plane traditionally used to fly to war zones came a day after Ms Pelosi infuriated Mr Trump by moving to delay his January 29 State of the Union speech in the House chamber.

The White House has not responded to Ms Pelosi’s leak claim.

Ms Pelosi and Mr Trump are at an impasse over funding the President’s wants for a US-Mexico border wall, which Ms Pelosi opposes.

The partial government shutdown has reached its 28th day.